Polyamide fiber

ABSTRACT

A conductive fibre having soil-hiding properties and good dye light fastness properties comprising a fibre-forming polyamide having an additive dispersed therein as a separate phase, the additive being derived from a boric acid and a poly(oxyalkylene) material of average molecular weight at least 600. The soil-hiding properties are produced on scouring the fibre.

This is a division, of application Ser. No. 304,867, filed Nov. 8, 1972.

The present invention relates to conductive fibres and to textilearticles derived therefrom.

The term fibre as used herein includes continuous filament and staplefibre.

Conductive fibres, particularly those also having soil-hidingproperties, are useful in carpets.

Due to their hydrophilic properties and ease of manufacture,poly(oxyalkylene) materials have been suggested and used as conductiveadditives in synthetic fibres. British patent specification No. 990,713discloses polyamide fibres having blended therein as a separate phase atleast 1% by weight of a poly(alkylene ether) glycol. It has been foundin practice that poly(oxyalkylene) additives, although confering usefulconductive properties to the fibre, have an extremely detrimental efforton the dye light fastness properties of the fibre.

We have now found that a useful conductive fibre, which overcomes theabove-mentioned deficiency of the prior art fibres, comprises afibre-forming polyamide having dispersed therein as a separate phasebetween 1% and 14%, preferably between 2% and 8%, by weight inclusive ofan additive which is derived from a boric acid and a poly(oxyalkylene)material of average molecular weight at least 600.

The separate dispersed phase in the fibre is in the form of smallparticles elongated in the direction parallel to the axis of the fibre.

The additive may be made by reacting boric acid with a poly(oxyalkylene)material having at least one free hydroxyl group. Examples of boricacids which may be used include orth-, meta- and pyro-boric acid.

Suitable poly(oxyalkylene) materials include ethylene oxide, propyleneoxide or ethylene oxide - propylene oxide condensation products.Residues of chain-initiating or coupling compounds may be present.Poly(oxyethylene) glycol is particularly preferred. It is preferred thatthe poly(oxyalkylene) material has an average molecular weight withinthe range 600 to 30,000.

The additive may be added as a poly(oxyalkylene) borate or in the formof the precursors. It may be incorporated in the fibre-forming polyamideat any stage of manufacture. Thus the additive may be incorporated inthe polyamide monomer prior to polymerisation or it may be incorporatedin the preformed polyamide immediately prior to extrusion of fibre.

Suitable fibre-forming polymers for use in the present invention arepolyamides such as poly(hexamethylene adipamide) or polycaproamide.

When fibres containing the additive particles are scoured, or subjectedto a similar wet treatment, some of the particles are extracted andleave internal voids which increase the covering power and soil-hidingability of the fibres.

The fibres of the present invention may optionally contain otheradditives such as antioxidants, stabilisers, delustrants or colouringmaterials. Such additives may be present in either or both of the twophases. Suitable antioxidants include hindered phenols such as, forexample, 2,4-dimethyl-6-α-methylcyclohexylphenol;1,1,3-tris-(2'-methyl-4'-hydroxy-5'-t-butylphenyl) butane and bis(2-methyl-4-hydroxy-5-t-butyl-phenyl) sulphide.

The following examples, in which all parts and percentages are byweight, illustrate but do not limit the present invention.

EXAMPLE 1

Poly(hexamethylene adipamide) containing approximately 7% by weight ofadditive was prepared by adding polyoxyethylene glycol of averagemolecular weight 1540 (250 parts) and ortho-boric acid (7 parts) tohexamethylene adipamide salt (4000 parts) in a autoclave and subjectingthe salt to polymerisation. The polymer was extruded at 290° C in theform of a carpet yarn having 68 trilobal filaments. The yarn was drawnand then immediately bulked by a stuffer-box crimping process and thenused in the preparation of a tufted carpet. The yarn had the followingproperties:

Decitex 2917, tenacity 2.3 g/dtex, extension to break 67.9% andmodification ratio 2.3. The yarn had an electrical resistance of 3.3 ×10¹¹, 3.9 × 10¹⁰ and 1.4 × 10⁹ ohms/cm at relative humidities of 21%,43% and 65% respectively.

Samples of the tufted carpet were scoured and then dyed at pH 6.5 at 95°C for 60 minutes with a range of acid dyestuffs. The dye light fastnessproperties of the carpet samples were measured and the results are givenbelow. For comparison, results are given for carpet samples made from(i) poly(hexamethylene adipamide) fibres and (ii) fibres made frompoly(hexamethylene adipamide) having polyoxyethylene glycol (PEG) ofaverage molecular weight 20,000 dispersed therein as a separate phase

    ______________________________________                                        Light Fastness                                                                                 Fibres                                                                        according                                                                     to present                                                                              Nylon   Nylon 6,6                                  Dyestuff         invention 6,6     and PEG                                    ______________________________________                                        Nylomine Yellow A-Gs                                                                           6         6       3                                          Nylomine Red A-2BS                                                                             5         6       3                                          Nylomine Blue A-2R                                                                             6-7       6-7     3                                          Nylomine Acid Yellow B-RD                                                                      5         5-6     3                                          Nylomine Acid Blue B-B                                                                         6-7       6-7     3                                          Nylomine Acid Green C-B                                                                        6-7       6-7     3-4                                        ______________________________________                                    

The above results show that the dye light fastness of nylon 6,6 fibrescontaining an additive derived from a boric acid and a polyoxyethyleneglycol are similar to those for normal nylon 6,6 fibres and are muchsuperior to those of nylon 6,6 fibres containing polyoxyethylene glycol.

Samples of the scoured and dyed carpets were tested for staticpropensity by measuring the voltage generated at 20% R.H. and 20° C.while walking on the carpet with shoes having composition soles. Thevoltages generated for nylon 6,6 containing the additive derived fromboric acid and polyoxyethylene glycol, nylon 6,6 and nylon 6,6containing polyoxyethylene glycol were 2.4, greater than 5.0 and 2.7kilovolts respectively.

A further sample of the scoured and dyed carpet, made from the nylon 6,6fibres containing the additive derived from boric acid andpolyoxyethylene glycol, was subjected to floor trails. After 28 daysuse, the carpet had a soiling additional density of only 0.197. Undercomparable conditions, a carpet made from nylon 6,6 fibres had a soilingadditional density of 0.285.

EXAMPLE 2

An additive was prepared by heating dry meta-boric acid (18.3 parts) andpolyoxyethylene glycol of average molecular weight 1540 (846.8 parts)for one hour at 230° C under atmospheric pressure. The additive formed acrystalline mass on cooling and was then chipped. The chipped additive(7 parts) was chip-mixed with poly(hexamethylene adipamide) chip (93parts). The mixture was melt-spun and then drawn to yield a 224 dtex, 20filament yarn. After scouring, the yarn had an electrical resistance,measured at 40% R.H., of 1.2 × 10¹⁰ ohms/cm.

EXAMPLE 3

Example 2 was repeated except that the additive was prepared by heatingpyro-boric acid (13.1 parts) and polyoxyethylene glycol of averagemolecular weight 1540 (675 parts).

The resultant yarn, after scouring, had an electrical resistance,measured at 40% R.H., of 1.2 × 10¹⁰ ohms/cm.

What I claim is:
 1. A conductive fibre comprising a fibre-formingpolyamide having dispersed therein as a separate phase between 1% and14% by weight inclusive of an additive which is derived from a boricacid and a polyoxyalkylene glycol of average molecular weight in therange up to 30,000.
 2. A fibre according to claim 1 in which thepolyoxyalkylene material is a polyoxyethylene glycol.
 3. A fibreaccording to claim 1 in which said fibre contains internal voids.